The effect of carbon nanofillers on the performance of electromechanical polyaniline-based composite actuators.

Different types of crystalline carbon nanomaterials were used to reinforce polyaniline for use in electromechanical bilayer bending actuators. The objective is to analyze how the different graphitic structures of the nanocarbons affect and improve the in situ polymerized polyaniline composites and their subsequent actuator behavior. The nanocarbons investigated were multiwalled carbon nanotubes, nitrogen-doped carbon nanotubes, helical-ribbon carbon nanofibers and graphene oxide, each one presenting different shape and structural characteristics. Films of nanocarbon-PAni composite were tested in a liquid electrolyte cell system. Experimental design was used to select the type of nanocarbon filler and composite loadings, and yielded a good balance of electromechanical properties. Raman spectroscopy suggests good interaction between PAni and the nanocarbon fillers. Electron microscopy showed that graphene oxide dispersed the best, followed by multiwall carbon nanotubes, while nitrogen-doped nanotube composites showed dispersion problems and thus poor performance. Multiwall carbon nanotube composite actuators showed the best performance based on the combination of bending angle, bending velocity and maximum working cycles, while graphene oxide attained similarly good performance due to its best dispersion. This parallel testing of a broad set of nanocarbon fillers on PAni-composite actuators is unprecedented to the best of our knowledge and shows that the type and properties of the carbon nanomaterial are critical to the performance of electromechanical devices with other conditions remaining equal.

Production and characterization of coaxial nanotube junctions and networks of CNx/CNT.

Novel coaxial structures consisting of nitrogen-doped carbon nanotube (MWNTs-CNx) cores with external concentric shells of pure carbon were produced by the pyrolysis of toluene over Fe-coated MWNTs-CNx. These materials were thoroughly characterized by SEM, HRTEM, X-ray diffraction, and TGA; a possible growth scenario for their formation is also proposed. In addition, these coaxial structures were able to form 2D and 3D covalent networks that mainly exhibited T-, Y-, and on-type morphologies. The two-step technique presented here could be further developed to fully control the growth of these new coaxial structures, study of individual junctions, and it could be used to create periodic nanotube networks, in which the heterocable structure could find applications in nanoelectronics.